1. Field of the Invention
This invention relates to a process for ring bromination of nitrobenzene which comprises contacting nitrobenzene with an alkali metal bromate and aqueous sulfuric acid wherein the weight percent sulfuric acid is in the range of about 52 to about 75 percent.
2. Description of the Prior Art
J. R. Johnson et al., Org. Syn., John Wiley, New York, N.Y., Collect., Vol. 1, 1956, page 123, state that nitrobenzene can be brominated using bromine and iron powder at temperatures of 135.degree. to 145.degree. C. A 65 to 75 percent yield was reported.
In C.A. 55:8348 d it is reported that B. V. Tronov et al. [Izvest. Vyssh. Ucheb Zaredenii i Khin i Khin Technology 3 872 (1960)] obtained 33 percent yield of bromonitrobenzene by brominating nitrobenzene using bromine, sulfuric acid, nitric acid and acetic acid over a period of 4.5 hours at 83.degree. C.
In C.A. 49:13133 f it is reported that B. V. Tronov et al. [Zhur. Obschehei, Khin. 24 1608 (1954)] reacted nitrobenzene with bromine using aluminum, sulfur and tellurium as catalysts.
K. Huthmacher et al., Synthesis (1978) 693 report that a mixture of potassium-peroxydisulfate and bromine produces a 30 percent yield of bromonitrobenzene using five percent fuming sulfuric acid at room temperature. In addition, they use the reagent AgO--SO.sub.2 --CF.sub.3 at room temperature and over a period of four to 16 hours to obtain 74 and 83 percent bromonitrobenzene.
D. H. Derbyshere et al., J. Chem. Soc. 573 (1950), report that nitrobenzene can be brominated by reacting nitrobenzene with bromine water and silver sulfate. The HOBr was prepared in situ. The reaction was carried over a period of 16 hours at room temperature.
F. L. Lambert et al., J. Org. Chem. (1965) 30, 304, report brominating nitrobenzene using 50 percent sulfuric acid by volume and n-bromo succinimide over a period of three hours at 85.degree.-90.degree. C. to obtain a yield of 70 percent.
W. Gottardi, Monatsch Chem., 99, 815 (1968) obtain a yield of 88 percent bromonitrobenzene over a period of five minutes at 20.degree. C. using dibromoisocyanuric acid in concentrated sulfuric acid (96 percent).